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Lecture 6

Lecture 6

Biological Sciences
Course Code
Rudy Boonstra

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October 16, 2007
Kenneth Boulding (1973) aptly describes the challenge we face (Quote).
It will be in this class. I will be here and so will Brendan. A number of you have to write
early so remind me next week, you will start at 8:00 and the rest of you will start at 9:00.
Bring your I.D.
I updated this lecture and I also put another article on there which will not be on the exam. It is
an inspiration story which is a Nobel Prize Winner, about Kapichi, who was an Italian child. His
life story is an inspiration to anyone especially anyone that is from an immigrant family. His
mother is a Bohemian and had been through many things including WWII. This child was on the
streets during the war and he survived. He is on the streets trying to survive and stealing to live
and eventually the police catch him and he goes into a hospital till he is 9 years old. They only
feed him bread and coffee and when the war ends his mom find him and they move to the U.S.
He eventually makes it to Harvard. You don’t have to read it if you don’t want to but it was in
the Time Magazine this morning.
This lecture will be on the exam. We will do a rapid snapshot of the world’s weather history up
until now. 4.5 billion years is a long time. I won’t do much of the geology but how it interacts
with the world’s atmosphere. You can see where most things are occurring, how the atmosphere
is formed, and how rapidly it can change. I gave you information about the earth 4.6 billion
years ago. 4th or 5th generation star, 13.7 billion years ago and we know that because of the
heavy elements. These elements are critical and they come from Supernova.
The moon is absolutely critical for stabilizing the earth. I told you about a book by Bill Bryson
and he talks about how special the earth is. The moon stabilizes the tilt and the rotation. That is
one thing. We are the exact right distance from the sun and we have this ‘blocker’ behind us
which is Jupiter which takes a lot of the hits. Chewmaker Levy (a comet) was interested in a
comet that was going to hit Jupiter but didn’t realize the force and they thought it would absorb it
but it didn’t. We are not however protected all the time.
The sun is more intense than 4.6 billion years ago and that is a problem. How do we protect the
place? It was dimmer then and hence the earth was colder unless we have the right gases.
BGYC58H3F.October,16, 2007 LECTURE 6 1

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Here is a complicated diagram that shows the formation of the earth 4.5 or 4.6 billion years ago.
The Geologic Time Scale is a summary. I have listed the major topics that I will cover:
1.Pre-Biotic Earth (slide) -> it isn’t very interesting because not much happens. Well, that
is before life gets going and lasts about 1 billion years.
2.Pre-Cambrian -> life gets going but in an atmosphere that is aerobic. In a world that is
very different than our own world and we know that because the organisms are
prokaryotes and basically once it gets going nothing really happens for a billion years.
You have single cell organisms almost like it can’t wait to get going then doesn’t do
much. Stromalights are colonies of aerobic organisms and they actually are still growing
at Sharp Bay. So you have a much more significant greenhouse effect because the sun is
dimmer so that effect has to compensate for the dimmer sun. It may in fact have been
that the bacteria that evolved aided and abetted this greenhouse effect by producing
methane. Remember methane is a strong greenhouse gas. You need a strong greenhouse
effect and they don’t know how much CO2 there had to have been in light of having a
dimmer sun to produce life and sustain it. Anywhere between 300 -> 1000 times the
a.Proterozoic -> another 2 billion years in the earth’s history (refers to the geologic
time scale). This is an expanding graph.
b.Early Biotic Earth -> relative to climate apparently photosynthesis (algae)
evolved about 2 billion years ago. This changes the equation and the equation is
one where you have a lot of CO2 + H20 -> C6H1206 + 602 and this changes the
picture entirely. Changes from an atmosphere where CO2 is a dominant gas to
one where eventually oxygen becomes a dominant gas but it takes a long time for
oxygen to become a dominant gas. Why? Because the world is full of things that
combine with oxygen. Any compound that is metal i.e. iron (has to be oxidized)
so it eats up the oxygen produced by the algae. Only when it is saturated can the
oxygen build up. So first you have to get rid of the compounds that gobble up
oxygen. You have to get rid of the methane and to do that you have to have CH4
+ 202 -> C02 + 2H20. Some of the C02 gets removed into biological tissue and is
incorporated into marine sediments and that leaves behind oxygen so it slowly
builds up.
c.Aerobic Earth takes up about 1.7 billion years ago and at that point carbon
dioxide levels dropped (uncertainty) and the estimated concentrations are between
10 -> 200 times present C02 levels. There is a lot of carbon dioxide and it is
creating the greenhouse gas effect so it goes into this area. It would run away as
the sun increases in intensity because it evaporates water vapour which is a major
greenhouse gas and if something didn’t gobble up carbon dioxide you would have
a Venus type planet. A lot of it went into beds of chalk, carbonates (set down by
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life in the world’s oceans), and some biotic processes take the carbon dioxide out
of the equation.
3.Phanerozoic (Eon) -> around 540 -> 600 billion years ago you get the evolution of multi-
cellular organisms. This is critical because now you have the possibility for more
detailed structure. They can process food and can be responsible for respiration, etc. So
now what happens in the atmosphere? There is a mechanism to process C02 more
quickly. There is evidence that it is too quick. It basically sucks too much C02 out of the
atmosphere and this precipitates the ice age. I didn’t mention the first one but this is
snowball earth 2. Huge ice sheets develop because there isn’t enough greenhouse effect
(40 million years before the start of the Phanerozoic) and it lasts 40 million years. It
can’t make the whole earth an ice sheet, but not really the whole earth. So there is
basically no atmosphere to warm. It was a result of biotic life sucking C02 out of the
atmosphere. What comes to the rescue? Volcanoes. Much of the stuff that is buried gets
stuck back into the atmosphere by volcanic activity. Again, the estimates are that another
greenhouse is created by C02 but we don’t know for sure.
4.Paleozoic -> now you have a series of radiations of life that occurs followed by extinction
events. Some extension events during this stage are severe and some are not. Some are
glaciation events and some are warming events. Some extension events are through to be
due to asteroid impacts. I want to dwell on the Carboniferous phase of the Paleozoic.
You have about 275 -> 350 million years ago the evolution of vascular plants. You have
ferns and licopodium developing and they are still in the forests around here. Here you
have a vascular system to move nutrients and water around, they are large, somewhere
erect, they have a root system, so you develop plants that have bio-mass and that is
needed to maintain structural integrity of the planet. A plant chemical develops that is
resistant to decay which is ‘ligman’. This provides strength to the plant and there isn’t
much that can chew it up so it resists decay when the plants die. So there is opportunity
for burial. When the plants are surviving there is a major glaciation going on because of
the position of the continents and they are like what we are experiencing now. They
alternate flooding large areas of continental shelf where the plants are and then they dry
out and it is good to grow. You have repeated flooding, burial, and new ground becomes
growing ground. This is the basis for the development of coal oil. So we are living off
sunshine buried in the past. The plants are made into coal, oil, and so on. We are about
here (points to graph). Levels are about 20 times higher and then they dropped and the
reason they dropped is the vascular plants. You are getting the one side of the equation
and C02 levels are plummeting. What happens then is that oxygen levels go through the
roof. If you look at the same time period you can see the carboniferous and the oxygen
levels go up to 30% so they are inversely related. As the C02 levels go down oxygen
increases. Thereafter oxygen levels plummet to reach their lowest level of about 12% by
about 100 million years ago. There is something going on at the time that we have high
BGYC58H3F.October,16, 2007 LECTURE 6 3
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